Deep vein thrombosis laboratory tests: Difference between revisions
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==Laboratory Findings== | ==Laboratory Findings== | ||
===D-Dimer=== | ===D-Dimer=== | ||
For a detailed discussion on D-dimer, please click'''[[D-dimer|here]]'''. | '''For a detailed discussion on D-dimer, please click '''[[D-dimer|here]]'''.''' | ||
[[D-dimer]] is a cross-linked [[fibrin degradation product]] and a marker of endogenous [[fibrinolysis]]. In the setting of ongoing thrombosis, | [[D-dimer]] is a cross-linked [[fibrin degradation product]] and a marker of endogenous [[fibrinolysis]]. In the setting of ongoing thrombosis, D-dimer's concentration is elevated in the blood and thus makes it a screening tool to rule out [[DVT]]. | ||
D-dimer is the "test of choice" in patients who are considered to be "low risk" according to [[Wells score for DVT|pre-test probability]]. D-dimer is more useful if its negative rather than positive. It has a great '''negative predictive value''' in low to moderate risk patients of DVT. If D-dimer is elevated, then [[DVT]] should be confirmed with [[Deep vein thrombosis ultrasound|ultrasound]].<ref name="pmid14507948">{{cite journal |author=Wells PS, Anderson DR, Rodger M, ''et al'' |title=Evaluation of D-dimer in the diagnosis of suspected deep-vein thrombosis |journal=N. Engl. J. Med. |volume=349 |issue=13 |pages=1227-35 |year=2003 |pmid=14507948 |doi=10.1056/NEJMoa023153}}</ref><ref name="pmid12755550">{{cite journal |author=Bates SM, Kearon C, Crowther M, ''et al'' |title=A diagnostic strategy involving a quantitative latex D-dimer assay reliably excludes deep venous thrombosis |journal=Ann. Intern. Med. |volume=138 |issue=10 |pages=787-94 |year=2003 |pmid=12755550 |doi=}}</ref> | |||
Interpretation may be improved by using age adjusted levels:<ref name="pmid24643601">{{cite journal| author=Righini M, Van Es J, Den Exter PL, Roy PM, Verschuren F, Ghuysen A et al.| title=Age-adjusted D-dimer cutoff levels to rule out pulmonary embolism: the ADJUST-PE study. | journal=JAMA | year= 2014 | volume= 311 | issue= 11 | pages= 1117-24 | pmid=24643601 | doi=10.1001/jama.2014.2135 | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=24643601 }} </ref> | |||
* Patients less than 50 years old: normal D-dimer is less than 500 µg/L. | * Patients less than 50 years old: normal D-dimer is less than 500 µg/L. | ||
* In patients 50 years or older: normal D-dimer is adjusted to be age multiplied by 10. | * In patients 50 years or older: normal D-dimer is adjusted to be age multiplied by 10. | ||
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Thus, D-dimer has a high sensitivity ('''sNOUT''') and low specificity ('''sPIN''') for [[DVT]]. This means that D-dimer is a better test for "ruling out" [[DVT]] rather than "ruling in". | Thus, D-dimer has a high sensitivity ('''sNOUT''') and low specificity ('''sPIN''') for [[DVT]]. This means that D-dimer is a better test for "ruling out" [[DVT]] rather than "ruling in". | ||
==== | ====D-dimer Elevation in Other Conditions==== | ||
D-dimer can be elevated in following conditions, which should be kept in mind while assessing | D-dimer can be elevated in following conditions, which should be kept in mind while assessing this biomarker in patients with suspected [[DVT]]: | ||
* Malignancy | * Malignancy | ||
* [[Disseminated intravascular coagulation]] | * [[Disseminated intravascular coagulation]] | ||
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* [[Atrial fibrillation]] | * [[Atrial fibrillation]] | ||
* [[Stroke]] | * [[Stroke]] | ||
=== Workup for Hypercoagulation === | === Workup for Hypercoagulation === | ||
Revision as of 14:48, 17 July 2014
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Overview
D-dimer is used in the diagnosis of deep vein thrombosis among patients with low or unlikely probability of venous thromboembolism.[1][2] While 500 ng/mL has long been the most commonly used cut off value for abnormal D-dimer concentration, recent studies suggest the use of an age adjusted cut-off concentration of D-dimer. The age adjusted cut-off value of D-dimer is 500 ng/mL for subjects whose age is less than 50 years, and the age multiplied by 10 for subjects older than 50 years.[3][4][5]
Laboratory Findings
D-Dimer
For a detailed discussion on D-dimer, please click here.
D-dimer is a cross-linked fibrin degradation product and a marker of endogenous fibrinolysis. In the setting of ongoing thrombosis, D-dimer's concentration is elevated in the blood and thus makes it a screening tool to rule out DVT.
D-dimer is the "test of choice" in patients who are considered to be "low risk" according to pre-test probability. D-dimer is more useful if its negative rather than positive. It has a great negative predictive value in low to moderate risk patients of DVT. If D-dimer is elevated, then DVT should be confirmed with ultrasound.[6][7]
Interpretation may be improved by using age adjusted levels:[8]
- Patients less than 50 years old: normal D-dimer is less than 500 µg/L.
- In patients 50 years or older: normal D-dimer is adjusted to be age multiplied by 10.
Specificity and Sensitivity
A large number of D-dimer assays are available and may vary in-between hospitals. In a meta-analysis of 217 studies involving DVT patients, the sensitivities of the D-dimer enzyme-linked immunofluorescence assay (ELFA) (96%), micro plate enzyme-linked immunosorbent assay (94%), and latex quantitative assay (93%; PE 95%) were superior to the whole-blood D-dimer assay (83%), and latex qualitative assay (69%). Because of this, ELISA assays are termed as "highly sensitive" and whole blood D-dimer assays is "moderately sensitive". Thus, D-dimer has a high sensitivity (sNOUT) and low specificity (sPIN) for DVT. This means that D-dimer is a better test for "ruling out" DVT rather than "ruling in".
D-dimer Elevation in Other Conditions
D-dimer can be elevated in following conditions, which should be kept in mind while assessing this biomarker in patients with suspected DVT:
- Malignancy
- Disseminated intravascular coagulation
- Elderly
- Infection
- Pregnancy
- Surgery/Trauma
- Inflammatory conditions
- Atrial fibrillation
- Stroke
Workup for Hypercoagulation
- Activated protein C resistance
- factor V Leiden mutation
- Protein C
- protein S, free and total.
- Antithrombin
- Lupus anticoagulant
- Anticardiolipin antibodies
- Plasma homocysteine values
References
- ↑ Wells PS, Owen C, Doucette S, Fergusson D, Tran H (2006). "Does this patient have deep vein thrombosis?". JAMA. 295 (2): 199–207. doi:10.1001/jama.295.2.199. PMID 16403932. Review in: Evid Based Med. 2006 Aug;11(4):119 Review in: ACP J Club. 2006 Jul-Aug;145(1):24
- ↑ Wells PS, Anderson DR, Rodger M, Stiell I, Dreyer JF, Barnes D; et al. (2001). "Excluding pulmonary embolism at the bedside without diagnostic imaging: management of patients with suspected pulmonary embolism presenting to the emergency department by using a simple clinical model and d-dimer". Ann Intern Med. 135 (2): 98–107. PMID 11453709.
- ↑ Douma RA, Tan M, Schutgens RE, Bates SM, Perrier A, Legnani C; et al. (2012). "Using an age-dependent D-dimer cut-off value increases the number of older patients in whom deep vein thrombosis can be safely excluded". Haematologica. 97 (10): 1507–13. doi:10.3324/haematol.2011.060657. PMC 3487551. PMID 22511491.
- ↑ Schouten HJ, Geersing GJ, Koek HL, Zuithoff NP, Janssen KJ, Douma RA; et al. (2013). "Diagnostic accuracy of conventional or age adjusted D-dimer cut-off values in older patients with suspected venous thromboembolism: systematic review and meta-analysis". BMJ. 346: f2492. doi:10.1136/bmj.f2492. PMC 3643284. PMID 23645857.
- ↑ Righini M, Van Es J, Den Exter PL, et al. Age-Adjusted D-Dimer Cutoff Levels to Rule Out Pulmonary Embolism: The ADJUST-PE Study. JAMA. 2014;311(11):1117-1124. doi:10.1001/jama.2014.2135.
- ↑ Wells PS, Anderson DR, Rodger M; et al. (2003). "Evaluation of D-dimer in the diagnosis of suspected deep-vein thrombosis". N. Engl. J. Med. 349 (13): 1227–35. doi:10.1056/NEJMoa023153. PMID 14507948.
- ↑ Bates SM, Kearon C, Crowther M; et al. (2003). "A diagnostic strategy involving a quantitative latex D-dimer assay reliably excludes deep venous thrombosis". Ann. Intern. Med. 138 (10): 787–94. PMID 12755550.
- ↑ Righini M, Van Es J, Den Exter PL, Roy PM, Verschuren F, Ghuysen A; et al. (2014). "Age-adjusted D-dimer cutoff levels to rule out pulmonary embolism: the ADJUST-PE study". JAMA. 311 (11): 1117–24. doi:10.1001/jama.2014.2135. PMID 24643601.